StuartO Posted February 13, 2020 Share Posted February 13, 2020 I’m exploring the idea of installing a 2 kw inverter close to my leisure batteries, so what size cables do I need to connect to the batteries? They might carry up to 100 amps for up to 15 minutes. Link to comment Share on other sites More sharing options...
spospe Posted February 13, 2020 Share Posted February 13, 2020 12 Volt Planet seems a good place to start looking. https://www.12voltplanet.co.uk/cable-sizing-selection.html Link to comment Share on other sites More sharing options...
StuartO Posted February 13, 2020 Author Share Posted February 13, 2020 Interesting website, thank you. Link to comment Share on other sites More sharing options...
Alanb Posted February 13, 2020 Share Posted February 13, 2020 StuartO - 2020-02-13 4:42 PM I’m exploring the idea of installing a 2 kw inverter close to my leisure batteries, so what size cables do I need to connect to the batteries? They might carry up to 100 amps for up to 15 minutes. Stuart, Your figure of 100A suggests that you are de-rating the inverter by about 50%. Assuming a generous 95% efficiency, a 2 kW inverter will draw about 175A at full load. This would suggest a minimum cable csa of 25 sq mm. From the thermal point of view, due to the limited time of use you may manage with 16 sq mm, but the larger cable would be kinder to your batteries, as the inverter will tend to draw more current as its input voltage falls. If your habitation batteries are leisure batteries as your post suggests, they may not like such high discharge currents. However if your habitation batteries are dual purpose such as the popular Varta LFD90, then no problem other than perhaps a slightly shortened battery life. Please note that battery capacities are generally quoted at the 20 hr rate. This means only 9A with a typical pair of 90 Ahr batteries. Observed capacity will be significantly reduced at higher discharge currents. Alan Link to comment Share on other sites More sharing options...
weldted Posted February 13, 2020 Share Posted February 13, 2020 I used a 2000 watt inverter for 7 years but I had it connected to the engine battery. Starter batteries are designed more for heavy discharge against a leisure battery which is more for small amounts of current over longer periods of time. Although there are dual purpose ones. The reason for using the engine battery is although I could power the microwave for around ten to twelve mins and still start the engine. If I needed the power for longer I would just run the engine. (With consideration to other campers) this way the battery would recover quickly when driving as opposed to draining the leisure batteries which given the poor rate of charge they get when driving would take longer to recover and have reduced power for the domestics. Link to comment Share on other sites More sharing options...
Bogfoldcruiser Posted February 14, 2020 Share Posted February 14, 2020 We just fitted a Victron 1200w inverter to replace the woefully small 300w fitted by Carthago , it comes with 1m of 25mm cable , I'd say a 2000w inverter would require 25mm cables fitted with good quality crimp or soldered fittings . Eddie Link to comment Share on other sites More sharing options...
John52 Posted February 16, 2020 Share Posted February 16, 2020 I usually find those fitting big inverters in a van don't really understand them. Wheras those who do understand them don't use them, and stick to gas for their heat. :-S Link to comment Share on other sites More sharing options...
Derek Uzzell Posted February 16, 2020 Share Posted February 16, 2020 A common reason for retro-fitting a high-output inverter is to power a 230V microwave-oven, and it might be worth quoting the following 2019 advice from the caravantalk forum Irrespective of wanting to run a microwave, a 1000w appliance wont just take1000w from the battery/batteries. I run a fleet of narrowboats and we did some tests last year. Conclusion was that to power an 800w microwave, the batteries had to give 4000w. Mind you, the 2500w inverters we use are fed by 4 x 110ah batteries and we always tell customers to run the boat’s engine to give the batteries a chance otherwise they'll run them flat. Link to comment Share on other sites More sharing options...
StuartO Posted February 16, 2020 Author Share Posted February 16, 2020 My thinking was that if I'm going to fit an inverter, I might as well have one big enough to deliver 1500w, for small cooking appliances, hair dryer etc, and then that I might as well round up a bit and choose pure sign wave output - and on browsing the options they mostly seem to come with suitable cables and these days have remote switching, so I could run mains cable from the output to a couple of dedicated mains sockets in a useful place - i.e. a quite separate 240v circuit from the MH's EHU circuit. But the benefit of having a convenient mains supply when touring using Aires etc, i.e. no EHU, would be quite limited and everything else (inc TV) runs on 12v, so I would probably be over egging things. Thanks for the comments - very useful. Link to comment Share on other sites More sharing options...
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